Machine Shop Yield and Cost - Productivity, Yield and Absorption Performance

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bruceliu222

#1
Medium size Scew Machine shop with 25 ACME 6~8 spindle machines and 10 Davenport machines which are struggling about the productivity, yield and absorption performance.
Scrap rate is at 5% while the productivity is <80%. Frankly the machines are relative old which most of them are 20~40 years old and we don't have a big replacement plan.
From the process improvement perspectives, what will be the most important sequences to improve above KPIs? What are the key data we need to collect?
 
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Michael_M

Trusted Information Resource
#2
Of coarse it depends on what you are after.

If you speed up the machines will your scrap rate increase beyond a reasonable level?

At a 5% scrap rate, are you confident that no 'scrap' part escapes

What is the actual performance at? 79% has a different answer than 60%.

Is the performance time set at what is actually doing or based on what you 'want it to do'?

Can the machines actually produce this requirement?

What (if any) is the on-going cost of maintenance?

Answering these questions may help to get you to an answer you want. I assume the machines are paid for so there really is less burden for the cost of the machine (no monthly payments) and this might help 'justifying' the reduced production cycle time.

If you got 'new' machines, can the burden of the machines be offset by the speed/quality improvement? Don't forget to add in less inspection time (if you can) because the newer machines should produce better parts
 
B

bruceliu222

#3
Thanks for your reply.
I am relatively new to this department so I am starting digging into more details. Here is what I observed in this beginning stage:
The setup time takes more than it was set up in the system. For example, some of the machine setup takes 50% longer than it was budgeted. We are working on the new training program to improve the setup efficiency, however it takes time.
Secondary, the TPY (throughput yield) is relatively low: while with 5% scrap, the TPY is actually about 85%. Operators do not strictly follow the 3-pan audit process well and parts rejection are caught in the final audit stage...
Third, the machine down time. With old machine, the downtime is also another contributor to drag down all the KPI performances.

What are your thoughts about the starting steps to approach the improvement in the machine shop?
 

Michael_M

Trusted Information Resource
#4
There are several issues that concern me here:

Operators do not strictly follow the 3-pan audit process well and parts rejection are caught in the final audit stage...
I am not sure exactly what you mean by this but if the 'scrap' parts are being caught in a final inspection this really concerns me. Inspection should be a double check not an actual check. One of the things I have heard and agree with is "100% inspection will not catch every part".

Mostly I would ask how the inspection process is being performed? Is it mechanical (say a camera system) or human interaction (human with a measurement device). Also, if parts are found in final inspection, would this not trigger some type of action "why did final inspection find bad parts".


the TPY is actually about 85%
The output is running at 85% and 5% scrap. Personally, I would worry about reducing scrap then worry about the 85%. I don't know the process you are running or the qty of parts run, but 5% scrap (to me) seems a bit high and should be the first 'fix' (if possible). I say if possible as some older machines just cannot hold some requirements. Are the machines capable of running the parts to the requirements?

Are the requirements acceptable? For example, long ago I had heard of something call 'SPC creep', where each year an improvement of CPK was required. After 10 years or so, a tolerance of .005, an easy tolerance to hold, became .0003 because they had to improve. Are the tolerances reasonable to your process?


The setup time takes more than it was set up in the system.
I have seen this as a common issue, we experience it here as well. We are addressing it in two ways. 1. We are looking at the setup time and asking 'is this realistic?' and 2. is there something we can do to speed up the setup time.

For question 1, if we give 1 hour for setup and everyone takes 3 hours (or the average is 3 hours) we change the setup time to 3 hours. On question 2, we look at cost vs. benifit, we setup a part once a year and the cost to speed up the setup is $500. We don't perform and suck up the 'extra' time. If however, for $500 we can save 25 hours a year then we will do so.

Just my thoughts, hope they help.
 
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